Method of forming a raised image



Oct. 4, 1960 c. F. CARLSON ETAL 2,955,052

METHOD OF FORMING A RAISED IMAGE Filed Jan. 3. 1956 2 Sheets-Sheet 1HIGH .1 VOLTAGE SOURCE HIGH VOLTAGE souczca INVENTORS CHESTER F- CAQLSONHARQLD BOGDONOFF Oct. 4, 1960 c. F. CARLSON ETAL 2,955,052

METHOD OF FORMING A RAISED IMAGE 2 Sheets-Sheet 2 Filed Jan. 3, 1956 'llllll llll INVEN T016 CHESTER F. (EARLS-ON HAROLD BQGDONOF F" .BY W

United States are "t .f

METHOD or FORMING A RAISED IMAGE Chester F. Carlson, Pittsford, andHarold Bogdonolf, Rochester, N.Y., assignors, by mesne assignments, toHaloid Xerox Inc., Rochester, N.Y., a corporation of New York Filed Jan.'3, 1956, Ser. No. 556,999

6 Claims. (Cl. 117-175) This invention relates in general to xerographyand, in particular, to producing relief images, characters, designs, andthe like, impressions therefrom, and other uses thereof.

Generally in the art of xerography, powder images are formed whichcorrespond to an original being reproduced or an object being examined.These images may be fused and thus made permanent, or they may beviewed, photographed, or the like, and then erased. This inventionconcerns itself with the deposition of additional particulate materialon the xerographic powder image to form improved relief images,characters, designs, and the like. The relief image, once formed, isthen utilized according to this invention to impress, transfer,partially or wholly, cut, emboss, of the like, a second surface. Thus,images formed according to this invention have been used to cutstencils, to form masters for the spirit duplicating process, to impressand emboss leather, metal, plastics, wood, linoleum and the like, totransfer material such as carbon and the like, and to form raised andreadable Braille characters, and the like.

It is therefore an object of this invention to devise an improvedprocess to xerographically form relief images, characters, designs, orthe like.

It is another object of this invention to devise improvedxerographically formed relief images, characters, designs, and the like.

It is yet another object of this invention to devise a novel process ofimpressing, embossing, cutting, transferring, or the like images,designs, characters, or the like using the novel relief xerographicimages.

It is still another object of this invention to devise new techniques ofmaster making for duplicating processes.

It is still another object of this invention to devise a novel processof impressing designs into surfaces.

It is still another object of this invention to devise a novel method ofcarbon printing.

It is still another object of this invention to devise a new techniqueof forming Braille images.

Additional objects of this invention will in part be obvious and will inpart become apparent from the following specification and drawings inwhich:

Figure 1, A, B, and C, illustrates an embodiment of xerographic steps toform a powdered image corresponding to copy being reproduced;

Figure 2 illustrates an embodiment of transfer of the powder image;

Figure 3 is an isometric partially cut away view of an embodiment of aheat tackifying unit and tackification of the transferred powder image;

Figure 4 is an isometric view of an embodiment of cascade deposition ofadditional material on the tacky image and an embodiment of cascademechanism;

Figure 5 is an embodiment of a pressure applying mechanism as anassembly passes through;

Figure 6 is a cross sectional view taken along line 6 of Figure 5 of theraised image;

2,555,552 Fatented Oct. 4, 1960 in Figure 7;

Figure 8-A illustrates separation of the assembly shown in Figure 7-A;

Figure 9 illustrates separation of an assembly in which partial transfertakes place such as with a carbon sheet;

Figure 10 illustrates separation of the image on its support base froman impressionable layer such as metal,

tile, or the like; and

Figure 11 illustrates the appearanceof an embossed and impressed layerfollowing the pressure step.

For a better understanding of this invention, reference is had to Figure1 wherein there is illustrated an embodiment of xerographic imageformation. The steps illustrated in this figure are Figure 1-A, chargingof a xerographic plate, Figure l-B, exposure and electrostatic imageformation of a previously sensitized plate, and, Figure 1-C, developmentof the plate carrying the electrostatic charge pattern or electrostaticimage with a fusible or resinous powder.

The plate in this figure is generally designated 11 and comprises alayer of photoconductive insulating material 12 overlying a conductivesupport base 13. The photoconductive insulating layer may comprise anyof a number of photoconductive insulating materials as, for example,sulphur, vitreous or amorphous selenium, selenium-tellurium mixtures,zinc oxide in a binder, or the like. Functionally, the photoconductiveinsulating material may be described as one able to retain, whileunexposed, an electrostatic charge on its surface for a sufiicientlylong period to allow exposure and development or other utilization of aformed electrostatic charge pattern on its surface and one which onexposure to activating radiation rapidly dissipates charge.

In Figure 1-A the charging or sensitizing step is illustrated using acorona discharge electrode generally designated 15 comprising a groundedshield 16 and corona discharge wires 17. Corona discharge wires 17 areconnected to a high voltage source 18 which supplies a corona generatingpotential to the discharge Wires. The potential supplied from highvoltage source 18 may be in the order of 6,000 to 10,000 volts and thevoltage may be direct, positive or negative, or alternating current.Generally, it is desirable to charge the surface of the photoconductiveinsulating layer 12 to from to 800 volts either positive or negativepolarity for image formation in xerography.

The corona discharge electrode 15 is driven by motor 20 along screw 21connected to both motor 20 and discharge electrode 15. Relative movementbetween the corona discharge electrode and the surface of the platebeing charged is desirable when the electrode covers only a smallportion of the plate surface. In this figure, movement of the electrodetakes place; whereas, in some instances the plate is moved while theelectrode is held stationary. When the electrode substantiallyencompasses and is able to sensitize substantially the entire imagebearing area a stationary electrode may be used with a stationary plate.

During charging, support or backing member 13 of plate 11 is generallymaintained at ground potential, and when because of the particularphotoconductive insulating material a charged plate is sensitive tolight, charging is carried out in darkness.

Figure 1-B illustrates exposure of a sensitive plate. In

this figure copy 22 to be reproduced is projected through lens 23 to thesurface of charged photoconductive insulating layer 12 overlying backingmember 131 of plate 11. Backing member 13 of plate 11 need not begrounded during exposure but may, if desired, be held at groundpotential. Exposure causes dissipation of charge in those areas struckby activating radiation such as light energy resulting in a chargepattern of electrostatic charges on the surface of the photoconductiveinsulating layer 12.

Figure l-C illustrates a possible development technique which may beused to make an electrostatic image pattern visible on the surface ofthe photoconductivej insulating layer 12 overlying backing member 13 ofplate 1 1 The particular type of development illustrated is generallyknown in the art as cascade development." In cascade development, whichis described in Walkup United States Patent 2,618,551, a mixture ofparticles 25 is presented to the image bearing surface. The particlesare generally fractio-nally electrostatically charged and theelectrostatic fields of force which exist between the charges on theparticles and the charges on the surface of the plate cause particledeposition in conformity with the electrostatic charge pattern on theimage bearing surface resulting in image 28.

Various known xerographic developers have been found to work Wellin'this invention in forming image 28 Such developers are availableunder the trademark Xerox and are sold as developer or toner by TheHaloid Company, of Rochester, New York. There are disclosed valuabledeveloper materials in Walkup United States Patent 2,618,551 and Walkupand Wise United States Patent 2,63 8,416. Other developers and tonersgenerally known to those in the art are also intended to be includedherein. Desirably the developer material which is used results in lowbackground particle deposition.

It is to be realized that the steps in Figure l are included herein forillustrative purposes. To carry out this invention it is desirable toform an image which may he tackified and which when tackified may befused. Although posure, X-ray exposure, or the like. Similarly, althoughcascade development is illustrated in Figure 1-C, other knowndevelopment techniques such as magnetic brush development, powder clouddevelopment, liquid spray development, or the like are intended to beincluded here in. Various other modifications which will readily occurto those skilled in the art are also intended to be included herein.

Reference is now had to Figure 2 wherein there is illustrated thetransfer of a developed visible image from the surface of a plate to anew support base. The plate 11 comprising photoconductive insulatinglayer 12 overlying conductive support base 13 has on its surfacefollowing development, for example, as illustrated in Figure l-C, apowder image 26 corresponding to the original copy to which the platewas exposed. I

To transfer this powder image to a new support base, such as a sheet orweb 27, sheet or web 27 may be positioned against the developed powderimage on the surface of plate 11 thereby sandwiching the developed imagebetween sheet 27 and plate 11. The assembly or sandwich is then movedbeneath corona discharge electrode 15 comprising corona discharge wires17 partially surrounded by grounded shield 16. Corona discharge wires 17are connected to high voltage source 18 which supplies a coronagenerating potential to the discharge wires. The assembly illustrated inthis figure is being moved from right to left beneath the dischargeelectrode by manually moving the plate carrying the image. 26 and sheet27. Following passage of the assembly beneath the discharge electrode,sheet or web 27 be separated from the plate and will carry on itssurface the transferred powder image 28.

The technique of transfer illustrated in this figure is generally knownin the art as electrostatic transfer. El ctrostatic ra f r, which is uly scribed. n Sch fi r UnitedStates Patent 2,576,047, is accomplishedthrough the deposition of an electrostiatic charge on the surface ofthe, tr, ster-sheet removed from the powder image. The polarity of thecharge deposited to bring about transfer is opposite to the polarity ofcharge on the electros-tatically charged particles comprising thedeveloped image, and, thus, the transfer charge acts toelectrostatically bind the charge particles to sheet or Web 27. Onseparation, the particles which form the image separate with sheet orweb 27 and electrostatically adhere to the surface of the transto heeThe technique of electrostatic transfer illustrated in this figure may,of course, be modified, and modifications generally known. to those inthe art are intended to be encompassed by this invention. Thus, forexample, other techniques of electrostatic charge deposition fortransfer purposes, such as frictional charging, or the techniquesillustrated in Mayo and Lewis United States Patent 2,684,902 or Saheland Mayo United States Patent 2,684,901, or the like may be used. Also,techniques which involve the use of electrostatic fields to causetransfer as, for example, positioning a field generating electrode aboveor in contact with the rear surface of the transfer base or the like areintended to be included herein.

Although electrostatic transfer is the preferred technique of transferin carrying out this invention, there is no intention to limit thisinvention thereto. Instead, all techniques. of transfer generally knownto the art which will allow this invention, to be carried out areintended to be included herein. Thus, techniques in which the powderedimage is transferred using pressure alone, or pressure combined withelectrostatics, orusing a transfer material which is adhesive onlyduring'the transfer step,

or the like may be used. in carrying out the process of this inventionand, accordingly, are intended to be encompassed within the scope ofthis invention.

It is also to be realized that the transfer step described in connectionwith Figure 2 maybe omitted entirely. The

purpose of the transfer step is to place the image on a new supportsurface. When it is desirable to use a plate to form additionalxero-graphic images, transfer of the powder image to a new support basesuch as paper or the like is desirable to free the plate for additionalcycles. However, when the plate itself is considered expendable with oneexposure and image development, the transfer step is'readily omitted,andthe steps of this invention may be carried out with the powderedimage remaining on the plate surface.

Reference is now had to Figure 3 wherein a tackifier and tackificationof the developed image is illustrated. In this figure, image 28 ispositioned on sheet or web 27 within a tackificr generally designated30. The taekifier 30- is'a heat fusing or tackifying device of the typedescribed in Sahel et a1. United States Patent 2,586,484. Tackifier 30comprises insulated cabinet 31 into which a drawer 32 having a handle 33is fitted. Positioned Within cabinet 31 are heating elements 34.

7 Drawer 32, which is more clearly illustrated in Figure 4, has fourWalled sides and two bosses 35 protrudinginward into drawer 32 from twoopposite walled sides. Positioned against the base or bottom of drawer32 is a frame 36"atta'ched-to drawer 32 by hinges 37: The frame 36 whenin its closed position, as illustrated, is held against-the base'orbottom of drawer 32 by grippers 38, and sheet27 carrying pattern orimage 28 is firmly posi tioned against the base of drawer 32 by frame36. Al-

though a particular device is illustrated in Figures 3 and '5 4, otherdevices as, for example, heated platens, infrared heating devices, orlike devices to accomplish tackification which will generally occur tothose skilled in the art are intended to be encompassed within the scopeof this invention. t t

Tackifica-tion of -'a powdered image isaccomplished when the imagebecomes a more liquefied adhesive unit. Although it is not intendedto.limit this invention ,to a particular mode of operation, it is nowthought that heat will act on the particles. to cause the viscositiesand surface tensions of theirnage particle materials to decrease therebyallowing the particles to flow together or coalesce as a more liquefiedadhesive single image body. I

In Figure 4 the cascading of particulate material 40 across the surfaceof tacky image 28 is illustrated. Drawer 32 has in this figure beenremoved from the fuser or tackifier and bosses 35 are positioned onbrackets 41 affixed to support arms 42. Particulate material 40 isillustrated in this figure as cascading across tacky image 38. Thematerial is madeto cascade across the image and across the surface ofsheet 27 by movement, controlled by handle 33, about the pivotpointsdefined by bosses 35. a

The base or bottom of drawer 32 is formed of a heat retaining materialsuch as Transite, a rocklike compressed asbestos material, or the like.'Frame 36 holds sheet 27 against the drawer base and this aids incontinuing image 28 in a tacky state. While image 28 remains tacky thecascading particulate material 40 becomes bonded to image areas and asubstantially uniform layer of particulate material 40 deposits on image28. The particles remain in position on image 28 substantially due tothe adhesive and tacky quality of the image. Although the image willgenerally remain tacky when exposed to atmospheric conditions followingheat tackification and, using the usual xerographic developer material,for about 30 seconds, contact with the heat retaining base of drawer 32keeps the image in a tacky state for as long as a number of minutes andthus aids in the production of a substantially uniform deposit ofparticulate material on-the image pattern 28.

Frame 36 accomplishes two purposes; it holds sheet 27 against the heatretaining base of drawer 32 and prevents the particulate material 40from cascading beneath sheet .27 by making intimate contact at its edgeswith the base of drawer 32.

Following the cascade step, through the tilting of the drawer backwardand forward while supported by brackets 41, sheet 27 is removed fromdrawer 32 and is allowed to cool and humidify. When cooled, the surfaceof sheet 27 may be brushed with a light brush such as a camels hairbrush or the like to remove loose particulate material.

The use of a drawer or tray similar to the one illustrated has beenfound'beneficial in forming the raised images of this invention. Anoticeable convenience is that particulate material 40 may be allowed toremain in the drawer at all times. When the drawer is tilted to causeparticulate material 40 to move to the rear of drawer 32, frame 36 maybe opened without disturbing particulate material 40. Also, during thetackification step, if the particulate material remains in the drawer,it is exposed to the heat of tackification, and this results, it ispresently believed, in thoroughly dry, free flowing particles.Humidified particles tend to cling together and distort theuniformity'of the flow pattern across the surface of sheet 27.Dehumidifiedparticles, on the other hand, tend to be deagglomeratedparticles and flow uniformly across the surface of sheet 27 as drawer 32is tilted upward and downward around pivot points or bosses 35.

, Particulate material 40 is formed of a material which is stable andinfusible at the tackifying temperature of the image, and may preferablycomprise glass or metal of rounded shape. The preferred material for theapplications of this invention are fine glass beads. A characteristicdesired of particulate material 40 is that it holds applicationsinvolved in this invention the best material used, and thus thepreferred particulate material of this invention is extremely smallbeads of glass having average diameter of 0.0034 inch. These beads willpass through .a .170 mesh screen and will be retained on a 200 meshscreen. Gla'ss beads supply the rigidity desired in the irnagesformedaccording to this invention, and the particular size beads preferreddeposit to produce a very elfective cutting, impressing, or embossing orpressure transfer relief image according to this invention. Using thepreferred glass beads, two passes of the beads over the tackyxerog-r-aphic developed image appear adequate.

For mimeograph stencil cutting, beads of diameter between .003 inch and.004 inch are preferred in order to cut through the stencil and stillnot be large as to reduce resolution of the image unduly. Thesediameters are preferred for cutting stencil sheets in which the stencillayer (consisting usually of an open mesh long fibre tissue paper filledwith a plasticized cellulosic ester or cellulose ether, or other plasticgel or wax) is substantially .002 inch "thick. From the experimentalwork it has been reasoned that beads approximately 0.001 inch greater indiameter than the thickness of the stencil layer or carbon layer of thespirit master set are generally preferred for the usual thin stencil orcarbon layers. For certain other purposes, such as embossing of leather,for example, sizes outside this range may sometimes be useful, al-

though this range is generally preferred in substantially allapplications to primarily maintain quality resolution.

It has also been found that the uniformity of particle diameter in acharge of beads '40 must be kept within rather narrow limits forsuccessful mimeograph stencil cutting, carbon and spirit duplicatingmaster pressing and the like. Thus, the diameters, from particle toparticle or head to head, must not vary more than plus or minus 7.5%from the average and, prefer-ably, shall not exceed plus or minus 5%from the average diameter. The importance of this is particularlyevident when a rigid roller system is used such as that shown in Figure5. It is evident that a few larger beads will tend to spread the rollersapart so the remaining smaller beads cannot penetrate adequately throughthe stencil (or apply adequate transfer pressure in case of carbonsheet, spirit duplicating carbons, and the like). The quantity of beadsheld in the tray is not critical. It should be sufiicient to cover thetacky image area during the cascading operation. The usual charge ofbeads placed in the drawer for covering a 9 x 12" image has been aboutgrams.

The sheet or web 2.7 carrying the developed image 28 is removed from thetray 32 following the cascade step illustrated in Figure 4. Generally,by the time removal of sheet 27 is completed or a moment after removalthe image pattern 28 will have hardened and there is thus formed a solidimage of hardened developer resin adhen'ng to support sheet 27 carryingon its exposed surface areas the beads or particulate material 40.

Reference is now had to Figure 5 wherein there is illustrated anembodiment of a pressure applying device and of a pressure applyingstep. In this figure, sheet 27, carrying on its surface fused image-28having on its surface a bound, substantially uniform layer ofparticulate bead material 40, is rolled against assembly 43, betweenrollers '45 and 46. In this embodiment manual drive to rotate rollers 45and 46 is supplied through crank 47 driving helical gears 49. Rollers 45and 46 are positioned and supported by support walls 48, and spaceadjusting means 50 are mounted in support Walls '48.

the stencil backing member.

A feature of the pressure applying device is that the pressure rollers45 and 46 are formed of a rigid'material I and of adequate diameter tolength ratio to resist bending or bowing under the rather high pressuresapplied across the full width as an assembly passes between.

In this figure, assembly 43 comprises a stencil duplicating set orspirit duplicating carbon set. Thus, assembly 43 comprises, as in theusual and commercially available stencil or spirit duplicating sets, twoindividual sheets or layers of material designated 51 and 52.. If sheetor web 43 is to be used in the spirit duplicating process, 51 representsthe carbon member of the spirit duplicating assembly and 52 representsthe master sheet. However, when forming a master for spirit duplicatingthe assembly may pass through the pressure device with the layersinterchanged. If 43 represents a stencilassembly to be used in stencilduplicating, 51 represents the wax covered stencil master sheet and 52represents Whether 43 represents the stencil or the spirit duplicatingassembly, the pressure supplied by rollers 45 and 46 to raised image 28and layer 40 on sheet 27 is applied to layer or sheet 51 of the assemblyand will cut or impress layer or sheet 51 of the assembly in the properfashion to form a master for the particular duplicating process forwhich assembly 43 is applicable. This will appear. more clearly below inconnection with Figures 6, 7, 7A, 8, and 8-A.

The rollers of the device of this figure are accurately and rigidlyspaced apart by a distance which is inthe order of 0.001 inch less thanthe combined thickness of the materials or layers without the imagepassing therebetween. Thus, in this embodiment they would be spaced inthe order of 0.001 inch less than the com bined thickness of the imagesupport layer and the sten-- cil assembly 43 whereby when the assemblyis passed through the rollers the. beads are forced to enter the stenciland perforate it. Spacing in stencil cutting is usually in the range offrom 0.009 to 0.010 inch. Upper roller 46 of the pressure rollers hasits bearing in slide blocks 44 which are slideable in vertical guidewaysformed in support walls 48. Shims are placed under these blocks 44 toset the spacing of the roller 46in relation to 45. Bearing screws 50'are then tightened to hold the rollers rigidly at the spacing which hasbeen set.

Reference is now had to Figure 6, which'is a sectional View taken alongline 6-6 of Figure 5. This figure diagrammatically illustrates the crosssectional view of the improved type of image of this invention. Theimage area, following the cascade step of Figure 4, comprises the fusedxerographic developer material 28 and the bound particulate material 40.Image 28 is fused to and supported on sheet or web 27. The particulatematerial, to some extent, rests on the surface of the fused image 28,and to some extent, is embedded into fused image 28. The material 40remains in position due to the adhering and/ or holding power of fusedxerographic image 28 which adheres and holds to both the particulatematerial 40 and support sheet 27. Although sheet or web 27 isillustrated in this figure as a thin layer of material, it is to berealized that the sheet or web may have substantial thickness and thatvarious thick"- nesses "of web material are intended to be encompassedby this invention.

Reference is now had to Figure 7 which is a cross sectional view ofassembly 43 when astencil is being formed taken along line 77 of Figure5. Layer 51 comprising a wax carrying fibrous layer of assembly 43 hasbeenpressed or impressed with the contours of the raised image on sheet27 as, for example, in areas 53 and 54 during passage through rollers 45and 46. In the impressed areas substantially all wax has been pressedaside and only fibers remain, whereas in the other areas substantiallythe original composition of this layer is unaltered. Layer 52willgenerally be shapedslightly as illustrated. in. this figureby. thepressure applyingstep.

layer 51 is a wax filled porous sheet.

However, that surface of layer. 52 which is pressed againstfthe solidroller will remain flat as appears in eatingmaster. Layer 52 in thisfigure represents the master sheet of the master set for the spiritduplicating process, and layer 51 comprises the carbon member of themaster set. Layer 51 comprises a support layer generally ofpapen'designated herein 70, and the carbon layerfil comprising a mixtureof wax and dye or dye intermediate. The raised image impresses layer 70and compresses layer 71 in areas of contact during passage betweenrollers and 46.

Reference is now had to Figure-8 wherein separation of the members ofassembly 43 representing a stencil master set in this embodimentcomprising layer 52, the backing sheet, and layer 51, the waximpregnated fibrous material, is illustrated. When separation takesplace, areas 55 and 56 comprising substantially the remaining waxtransfer from layer 51 to layer 52. Following separation, layer 51 is afinished master for the stencil duplicating process having the wax orwaxlike material removed in image areas and may be used on a stencilduplicating machine or manually to make stencil copies.

When assembly 43 comprises a mimeograph stencil set, The wax filling insuch an instance appears throughout the porous sheet and on both sidesof it. When pressure is applied, for example, as is described inconnection with Figure 5, areas of wax move laterally along the surfaceon which they are disposed and also through the porous sheet.

I On separation, as is illustrated in Figure 8, areas of wax againstwhich pressure was applied by the raised image to some extent adhere tolayer 52 and pull out from layer 51. Following separation, layer 51comprises a porous sheet coated with wax in all areas other than areasagainst which the pressure of the raised image was applied. In thoseareas substantiallyonly the porous sheet remains. the stencil master,ink travels through the porous sheet in areas of image and deposits on acopy sheet to form the stencil copy.

In Figure 8-A, there is illustrated separation of assembly 43. Assembly43 comprises a spirit duplicating master set and there is illustrated inthis figure separation of the-assembly illustrated in Figure '7-A. As inFigure 7-A, layer 52 represents the master sheet. Following separationthere is attached to the surface of master sheet52 dye or dyeintermediate 72 and 73 in image areas transferred from the carbon layer71 on the surface of sheet 51. The backing or support sheet for thecarbon dye or'dye intermedate layer is deformed or impressed in areas ofimage. The pressure applied transfers through support sheet 70 to thecarbon layer 71 on its surface. Image areas of carbon layer 71 thuspress firmly against the surface of the master sheet 52. On separationthe dye in image areas adheres to the surface of master sheet 52 therebyforming the master for the spirit duplicating processes which may thenbe used in the spirit or fluid duplicating processes in which a sheetof'paper or the like is moistened with 'a liquid in which'the carbonwaxmaterial is soluble resulting in spiritor fluid duplicating. copy whenthe moistened copy sheet is pressed against the master carrying the waxcarbon. image.

In Figure 9 partial transfer on separation following a pressure step isillustrated. The assembly, which is here'- in again designated 43, maycomprise layer 51, a normal carbon sheet comprising a support layer 75and a carbon layer 76, and layer 52; paper or similar sheet or webmaterial. Assembly 43 of Figure-9 would be shaped through: pressureapplying means such as the rollerillustrated. in Figure 5. or the;like.and thensepe When ink is applied to one side of armed. Portions ofcarbons 57 and 58 are transferred from layer 76, the carbon layer, tolayer 52 thus form ing the usual carbon copy as, for example, isobtained when using a typewriter or the like. The formation of carboncopies is similar to the formation of masters for the duplicatingprocess except that only partial transfer usually takes place and alsothe carbon sheet may be resused to make additional copies.

In Figure impressing of a surface is illstrated, and in Figure 11embossing of a surface is illustrated. Layer 62 ofFigure 10 and layer 63of Figure 11 have been carried through a pressure step in which sheet 27carrying fused image 28 and layer 40 of particulate material have beenpressed against and into the surface of layer 62 or layer '63. Thepressure step may be similar to the one illustrated in Figure 5. Todeform only one surface as in Figure 10 the sheet is impressed whilebacked by a rigid surface or while pressure is applied by rigid andsolid rollers. However, to emboss a layer as is illustrated in Figure11, the rear surface is positioned against a soft layer which acts as acushion to allow deformation or a relatively soft roller such as softrubber may be used. Following the pressure step, sheet 27 is separatedfrom layer 62 or layer 63. Layers 62 and 63 may represent asubstantially hard but deformable material such as a layer of soft sheetaluminum or hard rubber, wood, linoleum, plastics, or the like, or theymay represent a layer of soft material such as paper, cardboard, foil,plastics, or the like. When the surface carrying the image is pressedagainst material, such as layer 62, backed by a rigid backing only thesurface in contact with the image material will become indented;whereas, when pressed against a layer backed by a cushion which isdeformable and will allow the impression to affect the entire layer, theentire layer will be impressed and reshaped to conform to the image asillustrated in layer 63 in Figure 11. Thus, in Figure 10, followingseparation, areas 60 and 61 will appear depressed and will conform withareas of image comprising fused image 28 and layer of particulatematerial 40. On separation of the layer 63 illustrated in Figure 11,there will appear embossed areas 65 and 66 protruding in areas againstwhich the raised image on sheet 27 was pressed. The particular layermaterial which is impressed or embossed as discussed in connection withFigures 10 and 11 will depend on the particular use desired of theimpressed or embossed layer. Thus, for example, if it is desirable toform a design in plastics or in tile, plastics or tile would be used asthe impressionable surface. If it is desired to form an embossed leatherpattern, then an impressionable leather is pressed against the raisedimage. If it is desirable to form Braille characters on a sheet, then atypical Braille printing sheet such as Braille Paper available from thePerkins Institute, Watertown, Massachusetts, which appears to be manilatag stock, is pressed against raised Braille characters formed on thexerographic image support sheet. Similarly, for the various othermaterials which may be impressed or embossed the particular impressed orembossed end product desired will determine the particular layermaterial, which is pressed against the raised images of this invention.

Although all forms of transfer material have been used as sheet 27 incarrying out this invention, it has been found that harder sheetmaterial improves cutting, impressing, or pressure transfer inconnection with the step illustrated in Figure 5. It is presentlybelieved that improved impressions are formed because the raised imagewill not push as deeply into a hard layer as it will press into a softlayer and, thus, the raised image penetrates deeper and with greaterform into the impressionable surface during the pressure stepillustrated in Figure 5. Thus, it is more desirable to use a stiff sheetof paper as compared to a soft sheet of paper or plastic.

When sheet 27 is removed from the fuser or tackifier tray it isgenerally dry and thus subjected toelectrostatic effects which,interfere in the removal of loose beads. It has been found that allowingthe sheet to stand in normal room humidity for several minutes usuallyintroduces enough moisture so that the loose beads can be removed withlight brushing. A brush treated with an antistatic coating may also beused to remove the particles without the delay, and varying the transfersheet material also appears helpful.

Impressions have been improved noticeably when the image formed afterthe cascade step illustrated in Figure 4 is given a protective coating.The bead image may be sprayed witha fixative lacquer or plasticcomposition such as an aerosol spray of an acrylic resin in a volatilesolvent. A commercially available spray which has been found quiteeffective is sold under the name of Krylon. The spray not only forms aprotective coating but actually penetrates between the beads andreinforces the bond between beads and to the sheet. This may beaccomplished by manually passing the spray over the entire image sheet.Desirably, the deposition of spray should be uniform. In fact, the sprayplaces a protective coating over the image carrying sheet and over theimage. The improvement noticed in connection with the plastic coveredimage carrying sheet is twofold. First, the image impressed is improved,and, second, the protective plastic coating prevents the loss of beadsduring the impression or pressure step thereby further improving theimpressed surface and also aids in maintaining the image on the imagecarrying sheet for subsequent and additional utilization.

A desirable characteristic in carrying out this invention is that theassembly of elements'and the individual layers subjected to pressure beas thin and rigid as possible to cause the roller pressure to be fullytransmitted to the beads or raised image to thereby elficiently pressonly image areas into the impressionable layer. However, depending onrwults desired, a film cover sheet may be used to broaden the image andto prevent the beads or particulate material from becoming imbedded inthe impressionable sheet or layer. The use of a cushion sheet on theouter area of the assembly is questionable but may have value toovercome specific problems.

The rollers illustrated in Figure 5 are preferably accurately spacedrollers of rigid material. In carrying out this invention, a set ofsteel wringer type rollers were accurately and rigidly spaced apart apredetermined distance dependent on the thickness of the assembly to bepassed through. The spacing is chosen to be about 0.001 inch less thanthe combined thickness of the entire assembly including the imagesupport sheet without the image. Spacing is critical. Too great aspacing results in incomplete impressions and cutting; whereas, toosmall a spacing will distort the impression, make cranking difiicult,put undue strain on the rollers, and, if the impressionable material isa tearable material, tears will often appear. A test which has beenfound workable with stencil duplicating and spirit duplicating masters,for example, involves the passing of an assembly of the various layersof materials through the rollers, excluding the image, and adjusting thespacing of the rollers to a point of minimum spacing which will nottransfer stencil or spirit duplicating carbon or wax. Thus, when using aspirit duplicating master assembly, an image sheet similar to the imagesheet carrying the image is placed in contact with the master assemblyand is rolled between the pressure applying rollers. The rollers arethen adjusted to the minimum possible spacing at which carbon does nottransfer to the master sheet. This spacing, it has been found, is about0.001 inch less than the thickness of the assembly passed between therollers.

Rollers which have given good results comprise two 9-inch long solidsteel rollers 2 inches in diameter. It has been found that rollers 1 /2inches in diameter having a similar length tend to bend or bow underload and thus were unsatisfactory.

Pressure has also been applied to create the desired.

' applying the pressure between platens, or the like.

Generally, the developed xerographic image will be :in'

the order of 0.00025 inchto 0.00050 inch. The deposition of the beads orother particulate material results in an image substantally equal to thethickness of the fused image plus the thickness of the layer of the heador particulate material. Using this invention with the preferred beadmaterial the thickness of the image will range from .00365 inch to.00039 inch.

' Using normal and available xerographic developer materials it is usualto maintain the fuser or tackifier illustrated in Figure 3 in thetemperature range of 200 F. to 400 F. although controls exist toincrease ordecrease fus'er temperature depending on the developer beingused. This temperature range generally will not affect the image supportmaterial. The image on'its support base when using the usual tackifierheated to from 200 F. to 400 F. should be kept in the tackifier from 5to 45 seconds, depending on such factors as the particular xerographicimage material, the particular temperature of the tackifier, and thelike.

It has been found that movement of the assembly through the pressureunit illustrated in Figure 5 is generally not critical. Attempts,however, should be made to move the assembly through the unit at auniform rate of speed to thereby apply a uniform amount of pressure tothe raised image. Uniform pressure will uniformly impress the raisedcharacter into the impressionable surface.

While the present invention as to its objects and advantages as havebeen described herein has been carried out in specific embodimentsthereof, it is not desired to be limited thereby, and it is intended tocover the invention broadly within the spirit and scope of the appendedclaims.

What is claimed is:

1. The method of forming a raised image comprising xerographicallyforming a powder image of tackifiable Xerog'raphicdeveloper material ona support layer, tackifying the powder image, cascading across thetackified image thoroughly dried free-flowing solid particulate ma:terial. to. adhere a layer .of said particulate material only on. saidtackified image, said particulate: material being stable and unfusableat the tackitying t mperature of the tackified image. and beingsubstantially uniform in size and shape and having a diameter of no morethan about 0.004 inch, and then hardening the tacki-fiedimage therebybonding thereto the particulate material;

2. The method. of claim 1 in which the particulate material comprises.beads and in which the sizeof the heads is such that they will passthrough a mesh screen and be retained by a 200 mesh screen.

3. The method of claim'l in which the particulate material comprisesbeads and in which the diameter of the beads is in the size range ofbetween 0.003 and 00.04 inch.

4. The method of claim 3 in which the particulate ma.- terial comprisesglass beads.

:5. The method of claim 3 in which the particulate material comprisesmetal beads.

6. The method of claim '3 in which the diameterof the particulatematerial deviates from the average diam.

eter of the material by no more than -:7.5%.

823,445 Schramm June 12, 1906 1,146,853 Dick July 20, 1915 1,204,775Jacobsson Nov. 14,1916 1,593,439 Clark et a1. July '20, 1926 1,775,631Carlton Sept. 26, 1930 2,143,946 Hunter Jan. 17, 1939 2,354,049Palmquist July 18, 1,944 2,355,919 Lipsius Aug. 15, 1944 2,378,252Staehle et al. "June 12 1945 2,432,993 Jennings Dec. 23, 1947 2,512,348Lindsay June 20, 1950 2,573,881 Walkup et al. Nov. 6, 1951 2,681,473Carlson June 22, 1954 2,689,803 DAlelio Sept. 21, 1954 2,735,785 GreigvFeb. 21, 1956 2,738,727 'Dorman et a1. Mar. 20, 1956 2,769,391 Rosh-kindu-.. Nov. 6, 1956 FOREIGN PATENTS 20,542 Great Britain of 1904

1. THE METHOD OF FORMING A RAISED IMAGE COMPRISING XEROGRAPHICALLY FORMING A POWDER IMAGE OF TACKIFIABLE XEROGRAPHIC DEVELOPER MATERIAL ON A SUPPORT LAYER, TACKIFYING THE POWDER IMAGE, CASCADING ACROSS THE TACKIFIED IMAGE THOROUGHLY DRIED FREE-FLOWING SOLID PARTICULATE MATERIAL TO ADHERE A LAYER OF SAID PARTICULATE MATERIAL ONLY ON SAID TACKIFIED IMAGE, SAID PARTICULATE MATERIAL BEING STABLE AND UNFUSABLE AT THE TACKIFYING TEMPERATURE OF THE TACKIFIED IMAGE AND BEING SUBSTANTIALLY UNIFORM IN SIZE AND SHAPE AND HAVING A DIAMETER OF NO MORE THAN ABOUT 0.004 INCH, AND THEN HARDENING THE TACKIFIED IMAGE THEREBY BONDING THERETO THE PARTICULATE MATERIAL. 